Neither the pilot nor the biologist on board the Hughes 369D helicopter were injured but the moose's snout was hurt badly and the animal was euthanized at the scene, wildlife officials said.

The incident happened Saturday afternoon near Gustavus.

"I have never personally seen or heard of an injury of this type, caused to an animal by an aircraft," said Doug Larsen, regional supervisor for the Division of Wildlife Conservation. "It just had to be one of those quirky circumstance. Even dealing with bears and goats and moose and wolves, this is pretty unusual and truly a very unique situation."

Biologist Kevin White was aboard the helicopter, owned and operated by Ketchikan-based Temsco Helicopters. The identity of the chopper pilot was not immediately available. Larsen said the company has worked closely and successfully with the Division of Wildlife Conservation on outings to collar moose and capture grizzly bears.

Wildlife biologists are researching whether the environment in Gustavus can sustain such a dense moose herd.

White on Saturday was on a mission to tag a moose so that its movements could be tracked. He shot the moose with a tranquilizer dart, Larsen said, and the helicopter followed nearby in "a pretty confined area" so that the animal would not slip into a tight space or collapse in water and drown.

"The moose would start to move, and then the helicopter would back off and try to keep the moose out in the open," Larsen said.

Instead of moving toward open space, the darted moose headed for the helicopter.

"As the animal got closer and closer to going down, an animal sort of loses its thinking - its ability to rationalize what's in its best interest," Larsen said. "Apparently at that point the moose ... decided to come toward the helicopter. As the moose came toward it, the pilot couldn't maneuver out of the way, and the moose ran into the tail rotor."

The chopper was hovering, Larsen said. With the tail rotor damaged, the pilot was able to abruptly bring the craft down without causing greater damage.

The moose's snout collided with the chopper's tail rotor.

"It was really beyond help at that point," Larsen said. "When it hit its nose, it basically chopped off the end of its nose. It was really severely injured."

The helicopter had to be lifted from the scene because, without a tail rotor, it could not fly.